1. Field of the Invention
The present invention relates to a jig for a spinning test of a ceramic rotor, capable of dynamically balancing an assembly of the jig and the ceramic rotor mounted in the jig, and further relates to a method of dynamically balancing the jig-rotor assembly.
2. Related Art Statement
Various rotors for turbochargers and axial-flow turbines, and for other applications are known. In recent years, there is an increasing tendency that such rotors are formed of ceramic materials which are excellent in heat resistance and are lightweight. Commonly, these ceramic rotors are produced by adding an organic binder to a selected ceramic material, injection-molding the ceramic-binder mixture to a desired configuration, removing the binder from the molded piece, and finally firing the molded piece. For assuring high quality and reliability of the ceramic rotors, all of these products are subjected to non-destructive and spinning tests.
In a spinning test of a ceramic rotor, the rotor is spun or rotated at a high speed to check if the rotor meets prescribed standards of performance. Generally, the ceramic rotor to be tested is mounted in a suitable metal jig of a generally cylindrical shape having a fixing hole, such that the rotor is fixed in the fixing hole by means of a shrink fit or a press fit. The jig is attached to a driving shaft of a spinning tester. To avoid vibrations of an assembly of the ceramic rotor and the jig at a high testing speed, the assembly must be dynamically balanced prior to the spinning test. To dynamically balance the jig-rotor assembly, a method is known, wherein the jig with the ceramic rotor fixed thereto is mounted on a dynamic balancing machine to find a dynamic unbalance. The jig-rotor assembly is dynamically balanced by cutting off necessary amounts of material from appropriate portions of the metal jig.
3. Problems Solved by the Invention
However, such a known conventional balancing method wherein the jig-rotor assembly is dynamically balanced by removing material from a metal jig, is time-consuming and cumbersome, and requires a high level of craftsmanship. Furthermore, the number of times that a metal jig can be used is limited because of repeated cuts of material from the jig for a plurality of individual rotors. Consequently, the known method is disadvantageous in terms of testing efficiency and economy, particularly where a large number of ceramic rotors must be tested. This is a problem encountered in the prior art, that must be solved.
Another problem associated with the above-indicated known method lies in the requirement that the metal jig in which a ceramic rotor is shrink-fit should be heated again to permit the ceramic rotor to be removed from the jig after a spinning test of the rotor is completed. The procedures for mounting and dismounting the ceramic rotor from the metal jig also require a lot of time. Further, the heating and shrinkage of the metal jig for mounting the ceramic rotor, and the subsequent heating for removing the rotor, will cause the metal jig to be oxidized due to exposure to a high temperature. As a result, the life expectancy of the metal jig is further shortened.